This invention relates to active matrix devices and more particularly, but not exclusively, to active matrix liquid crystal displays (AMLCDs).
Active matrix devices, such as AMLCDs, are used in an increasingly wide variety of products, including consumer electronics, computers and communication devices. The structure of an AMLCD is described for example in U.S. Pat. No. 5,130,829 (our ref PHB 33646), the contents of which are incorporated herein as reference material. Active matrix devices are often included in portable products where the size and compactness of the device are particularly important considerations.
AMLCDs comprise a rectangular array of pixel elements addressed by means of row and column electrodes. The row electrodes are driven with row selection signals generated by a row driver circuit, while the column electrodes carry video information generated by a column driver circuit. Each pixel element includes a control element, such as a thin film transistor, connected to a row electrode and a column electrode. The row and column driver circuits are arranged adjacent respective perpendicular edges of the display.
The use of single-sided AMLCD addressing in rectangular tiled displays is described in xe2x80x9cManufacturing of Large Wide-View Angle Seamless Tiled AMLCDs for Business and Consumer Applicationsxe2x80x9d by R. G. Greene et al, pp191-4 of the Proceedings of the IDMC 2000 Conference in Seoul, Korea in September 2000.
The present invention provides an active matrix device comprising a supporting plate, an array of control elements, a set of row address conductors on the plate for addressing the array to which selection signals are applied by a row driver circuit, and a set of column address conductors on the plate to which data signals are applied by a column driver circuit for conduction to the array, wherein connection from the respective driver circuits to at least some of both sets of address conductors is via the same side of the array, the profile of the plate around the other sides of the array being non-rectangular.
In the existing AMLCD configuration described in U.S. Pat. No. 5,130,829 as referred to above, the screen is rectangular as connections to the row and column address conductors must be disposed along orthogonal edges of the active matrix. This restricts the design freedom of product manufacturers, particularly for relatively small products, as the choice of screen shapes available is limited and also space must be provided around the border of the screen on two orthogonal sides to accommodate the driver circuits and connections thereto from the screen.
Connection to at least some of both row and column address conductors of an active matrix device of the invention is via the same side of the matrix. Thus the space occupied on the other sides of the matrix by connectors and/or driver circuits can be substantially reduced or eliminated, allowing much greater flexibility in designing a product including such a device. Furthermore, non-rectangular devices can be fabricated, without requiring a large border area, as the device shape is not constrained by the need to have driver connections along two orthogonal sides. The use of single-sided addressing may also enable the total border area occupied by connectors and/or driver circuits to be reduced, enabling the overall size of a product to be smaller. This is especially desirable in portable products such as mobile telephones or personal digital assistants (PDAs) for example.
Connection from the row driver circuit to the row address conductors may be via respective connectors which are substantially parallel to the column address conductors within the array area. Alternatively, connection from the column driver circuit to the column address conductors is via respective connectors which are substantially parallel to the row address conductors within the array area.
Depending on the shape of the array, connection to some or all of both sets of address conductors is via the same side of the array. For example, if the side of the array adjacent the driver circuits is curved, it may be preferable to connect directly to all of the column conductors and the closest row conductors via the edge of the array, with additional connectors which extend substantially parallel to the column conductors within the array area being provided for connection to the remaining row conductors. Alternatively, connection to all the address conductors may be via the side of the array adjacent the driver circuits.
The profile of the plate may be substantially symmetrical about an axis, or about perpendicular axes. For example, an ellipsoid or oval shape may be desirable in some circumstances. Furthermore, the array of control elements may be non-rectangular. Preferably, the array is substantially symmetrical about an axis, or substantially symmetrical about perpendicular axes.
Preferably, the active matrix device forms part of a liquid crystal display. In particular, it may be a reflective or transflective type of display. In these configurations, the introduction of the additional connectors to the row or column address conductors need not reduce the aperture of the pixels, as they may be obscured by the reflective part of each pixel.
The invention further provides a method of constructing an active matrix device comprising cutting a pre-formed active matrix device, the pre-formed device comprising a supporting plate, an array of control elements, a set of row address conductors on the plate for addressing the array to which selection signals are applied by a row driver circuit, and a set of column address conductors on the plate to which data signals are applied by a column driver circuit for conduction to the array, wherein connection from the respective driver circuits to at least some of both sets of address conductors is via the same side of the array, the cutting step resulting in the profile of the plate around the other sides of the array being non-rectangular. Thus, devices may be manufactured from a stock of standard blanks and shaped individually as appropriate.
A laser may be used in the cutting step. In an AMLCD, the plate (and a second plate spaced therefrom) is typically formed of glass, which can be reliably fractured along straight lines using a xe2x80x9cscribe and breakxe2x80x9d technique. However, more complex and/or curved shapes may be more readily cut in glass and other suitable plate materials by utilising laser scribing.